The present invention relates to portable power tools and in particular to a novel auxiliary handle for supporting the forward end of a power tool having an elongated housing.
As is well known, various portable power tools comprise a relatively elongated housing in which the mass of the tool driving means is distributed. The mass distribution of such power tools contributes to a center of gravity which is located at a distance from the standard rearwardly located handle of such a tool and results in a relatively large moment relative to the handle. This fact results in a tool which is often awkward and difficult to control by way of a single handle situated at the rearward portion of the housing of the tool. This controllability problem is important in applications where it is necessary to keep the drill bit of such a power tool in a substantially perpendicular orientation relative to a working surface. This problem is particularly acute with power tools such as rotary hammers or hammer drills wherein the tool is adapted to impart both axial and torsional loads to a drill bit designed to perform work on relatively hard working surfaces.
In attempts to alleviate the above noted problems and contribute to a more controllable power tool, various auxiliary handles have been provided at or near the forward section of the elongated tool housing to allow the operator to support the power tool at a second point thereon. Additionally, such handles have typically included means allowing them to be rotated within a plane normal to the axis defined by the tool bit. Such a feature allows power tools equipped with such a forward auxiliary handle to be utilized in various environments while additionally providing the operator with a limited degree of freedom in orienting the handle to his liking.
However, prior auxiliary power tool handles of the above-described type possess certain limitations which do not totally resolve the problems associated with such tools. More specifically, such auxiliary tool handles are rotatable only in a single plane situated perpendicularly of the axis defined by the drill bit of such a tool. A user of such a handle is therefore limited in his choice of handle positions. This situation may restrict the use of such an auxiliary handle in certain limited space applications. Moreover, the load placed upon the tool by a user through such an auxiliary handle creates a moment about the drill bit axis which introduces additional problems in controlling the point of contact of the drill bit with a work surface as well as the orientation of the entire tool during a drilling or hammering operation. Therefore, such prior known auxiliary handles do not totally resolve the controllability problems associated with the use of portable power tools having elongated housings.
It is, therefore, desirable to provide an auxiliary power tool handle which reduces the moment about the axis of the drill bit of a power tool created by exerting a forwardly directed force upon the handle parallel to the axis of the drill bit. It is further desirable to provide such an auxiliary handle which is readily positionable in more than one plane to allow the load placed upon the handle to be directed as desired and the handle to be utilized more readily in limited space situations. Moreover, it is desirable to provide such a handle which is of a simple construction, is convenient to use, and is easily attachable and positionable relative to the housing of a power tool.
The auxiliary handle according to the present invention is positionable in three dimensions relative to the axis of the drill bit extending forwardly of the tool housing. The handle includes a pair of clamping jaws which defines a concave annular recess in which a complimentary shaped annular split collar is carried. The collar defines an inner surface which is cylindrical and an outer surface which is convex in shape so as to define the zone of a sphere. The collar is adapted to receive and engage a cylindrical barrel portion of the tool housing and may be clamped or secured thereto through the imposition of a clamping force generated by a threaded stud which is affixed to and rotatable with the handle. This novel auxiliary handle arrangement allows the handle to be rotated 360.degree. about the axis of the drill bit, as well as pivoted both longitudinally and transversely relative to the drill bit by moving the clamping jaw/handle combination about the annular collar prior to the imposition of a clamping force thereto. As such, the present invention provides a user with a more versatile auxiliary grip for a power tool, as well as a secondary support for the tool which minimizes the moment generated by loads placed upon the handle by the user.